The Combine Tool is a Shape Operation that combines two or more features into one new feature. The attribute data for the new feature will be automatically filled in using the feature that was first selected.
Before you can use the Combine Tool, you must first select two or more features in the feature layer of your choice. Remember that the data from the feature selected first will be put into the new combined feature. After your features are selected, the Combine button will be available to you in the ribbon bar. Clicking the button will open an attribute window showing all the data from the first feature selected. You can at this point edit any of the data before continuing. Once you are finished with the attribute window, click on Save Edits to commit the change. If an area feature is combined with another area feature and they are snapped together, the lines between them will disappear, making a new shape.